The invention relates to a floater-type heat treating furnace, especially the floatation-type pressure pads which are designed to support a continuous strip of material, e.g. aluminum or copper, on a fluidized bed as the strip travels through the furnace.
Pressure pads are widely used to float strips of soft, easily deformable materials, under low tension, through heat treating furnaces, since such materials are susceptible to being damaged, if they are allowed to contact rigid rolls that are oftentimes used to physically support and guide strips of metal through a furnace. The pressure pads are normally arranged in pairs which confront the pathway or pass line along which the strip moves through the furnace. Each pad generally comprises two parallel rows or lines of jet nozzles which extend longitudinally of the pad and which are designed to direct streams or jets of gas in a normal direction against the moving strip. Each row of jet nozzles may consist of a number of spaced and aligned perforations, or a single, continuous slit or slot which is coextensive with the width of the strip. In either case, the lines of jet nozzles of opposing pads are designed to create a static field pressure upon which the strip is supported.
It has been found that the aforementioned conventional pressure pads do not adequately support the strip which becomes wavy in a crosswise direction and assumes the shape of the wing of a seagull throughout its width, i.e. the center and opposing marginal edges of the strip are closer the vertically lowermost pressure pads than the portions of the strip between the center and marginal edges. The invention is designed to eliminate this problem by the provision of an improved pressure pad which supports the strip in a flattened condition.
Briefly stated, the invention is in a pressure pad which comprises two rows or lines of jet nozzles for directing streams or jets of gas against a strip of material which is passing nearby. The lines of jet nozzles are made to converge towards each other adjacent opposing ends of the pads, so that the streams or jets of gas emitting from the converging lines of jet nozzles, each have a component of force in a laterally outward direction tending to stretch the strip in a crosswise direction.
Another aspect of the invention is the offsetting of adjacent pairs of confronting pads to produce a wave lengthwise in the strip to help flatten the strip.